It took me a long time as a grownup to make real friends. A lack of real friendship left a gaping hole in my life and a huge stress on my marriage. It’s just too much to ask one person to be everything you need. Then I met Fairy Tale Mom, and everything changed.

A year later, Gotcha Baby and I crossed the line from friendish to all out friends. And last year, Hoosier Party Girl went from barely an acquaintance to one of my dearest friends. A few months — and one disastrous craft night later — Indy With Kids was added to the fold.

So, I spent more than a decade of adulthood with zero real friends, and added four of the best ones a girl could have in under four years. And, then I read a book that explained exactly how that happened. Yeah, sometimes I work backwards. MWF Seeking BFF is the memoir of one woman’s search for a true friend.

Rachel Bertsche writes the story of her yearlong commitment to 52 friend-dates, along with a healthy dose of research on friendship, attachment, and the science behind relationships. As I read, I picked out a bit of a formula for best friends. One that I could see in each of the relationships I had developed through the last few years. I think if you have two out of the four, you’d be well on your way to a serious friendship.

So, here you go! How to make your very own grownup friend:

Spend time together at least twice a month for three months. This one is key — regular contact builds a strong bond. Ours started with the occasional girls’ night out, but our friendships grew and really progressed when we added a monthly Margarita Monday. We were seeing each other for other activities at least once a month, and the addition of a 2nd, dedicated night for friends catapulted us to best friend level.

Do something together that’s out of your comfort zone (physical activity is great for bonding.) None of us are really very good at moving outside of our comfort zone (well, except for FTM anyway), but circumstances did offer opportunities to push our boundaries together — rock climbing, ziplining, terror-filled near-misses on a road trip. Apparently, adrenaline increases attachment. (And I’m an ardent abuser of alliteration.)

A common enemy is more binding than common interests. We came together through our shared love of blogging and children, but were bonded by our shared hatred of spam, social media douchebags, and the stupidity of the men around us. Talking about what you don’t like in addition to what you do like can build stronger bonds. The trick is to keep a good balance so your interactions don’t become negative.

Laugh together. Our girls’ nights include plenty of complaining and drinking, with a healthy dose of laughter. Real, live laughing out loud increases endorphins and lowers the production of stress-inducing hormones. Laughter is an actual, physical release that everyone needs daily. That’s science, you guys. Getting a healthy dose of laughter and endorphins every month on 3rd Monday has become an addiction, and these friends I’ve built as a result are a necessary part of my daily life.